Imaging lens unit

ABSTRACT

Disclosed herein is an imaging lens unit, including: a first lens having a positive (+) power; a second lens having a negative (−) power; a third lens selectively having one of a positive (+) and negative (−) power; a fourth lens having a negative (−) power; and a fifth lens having a negative (−) power, wherein the first lens, the second lens, the third lens, the fourth lens, and fifth lens are arranged in order from an object to be formed as an image, and the fourth lens is concave toward an image side.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2011-0103101, filed on Oct. 10, 2011, entitled “Image Lense Unit”,which is hereby incorporated by reference in its entirety into thisapplication.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an imaging lens unit.

2. Description of the Related Art

Recently, due to the advancement in technology, mobile terminals such asmobile phones and personal digital assistants (PDAs) are currently usedfor not only making simple phone calls but to also perform functions formulti-convergence such as playing music or movies, watching TV, andplaying games. One of the leading factors for such multi-convergence isa camera module.

In general, a compact camera module (CCM) has a compact size and isapplied to portable mobile communication devices such as camera phones,PDAs, and smartphones and various information technology (IT) devicessuch as toy cameras. Presently, CCMs are being installed in variousdevices in order to meet demands of consumers having specificpreferences

As the CCMs have to perform various functions using a compact opticalsystem, various techniques are used to make the modules slim. Inaddition to the slim size, demands for image quality of the compactoptical system are also increasing, and thus development of slim opticalsystem providing a high image quality is required.

Thus, recently, an imaging lens unit constituting a high resolutionimaging lens by using five lenses having positive (+) refractive powerand negative (−) refractive power has been developed.

However, the imaging lens unit having five lenses described above cannotprovide normal optical characteristics or aberration characteristics asdesired by users according to predetermined conditions.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to provide an imaginglens unit having five lenses and satisfying conditions of opticalcharacteristics desired by users and showing excellent aberrationcharacteristics.

According to a first preferred embodiment of the present invention,there is provided an imaging lens unit, including: a first lens having apositive (+) power; a second lens having a negative (−) power; a thirdlens selectively having one of a positive (+) and negative (−) power; afourth lens having a negative (−) power; and a fifth lens having anegative (−) power, wherein the first lens, the second lens, the thirdlens, the fourth lens, and fifth lens are arranged in order from anobject to be formed as an image, and the fourth lens is concave towardan image side.

The fourth lens may be a meniscus-shaped lens.

An Abbe number v4 of the fourth lens may satisfy the followingconditional expression:

0<v4<30.

The second lens and the fourth lens may be formed of a high dispersionmaterial.

An Abbe number v1 of the first lens may satisfy the followingconditional expression:

50<v1.

An Abbe number v2 of the second lens may satisfy the followingconditional expression:

0<v2<30.

The first lens may have a convex form toward an object side.

The second lens may have a concave form toward the image side.

The fifth lens may have an inflection point toward the image side.

The third lens may have negative (−) power.

The third lens may have positive (+) power.

The imaging lens unit may further include an aperture stop disposed infront of the first lens to adjust a light amount.

The imaging lens unit may further include an aperture stop disposedbetween the first lens and the second lens to adjust a light amount.

The first lens, the second lens, the third lens, and the fourth lens mayall be made of a plastic material.

A total focal length f of the imaging lens unit, a curvature radius r7of the fourth lens on the object side, and a curvature radius r8 of thefourth lens on the image side may satisfy the following conditionalexpression:

0<(r7+r8)/(r7−r8)<−2.5.

A total focal length f of the imaging lens unit and a distance tt from avertex of the first lens on the object side to the image side maysatisfy the following conditional expression:

0<tt/f<1.3.

An Abbe number v1 of the first lens, an Abbe number v2 of the secondlens, an Abbe number v3 of the third lens, and an Abbe number v4 of thefourth lens may satisfy the following conditional expression:

0.7<(v1+v2)/(v3+v4)<1.0.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the U.S. Patent and TrademarkOffice upon request and payment of the necessary fee.

FIG. 1 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a first embodiment of thepresent invention;

FIG. 2 is a graph showing aberrations of the imaging lens unit accordingto the first embodiment of the present invention;

FIG. 3 is a graph showing coma aberration of the imaging lens unitaccording to the first embodiment of the present invention;

FIG. 4 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a second embodiment ofthe present invention;

FIG. 5 is a graph showing aberrations of the imaging lens unit accordingto the second embodiment of the present invention;

FIG. 6 is a graph showing coma aberration of the imaging lens unitaccording to the second embodiment of the present invention;

FIG. 7 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a third embodiment of thepresent invention;

FIG. 8 is a graph showing aberrations of the imaging lens unit accordingto the third embodiment of the present invention;

FIG. 9 is a graph showing coma aberration of the imaging lens unitaccording to the third embodiment of the present invention;

FIG. 10 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a fourth embodiment ofthe present invention;

FIG. 11 is a graph showing aberrations of the imaging lens unitaccording to the fourth embodiment of the present invention; and

FIG. 12 is a graph showing coma aberration of the imaging lens unitaccording to the fourth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings. In thespecification, in adding reference numerals to components throughout thedrawings, it is to be noted that like reference numerals designate likecomponents even though components are shown in different drawings. Inthe description, the terms “first”, “second”, “one surface”, “the othersurface” and so on are used to distinguish one element from anotherelement, and the elements are not defined by the above terms. Indescribing the present invention, a detailed description of relatedknown functions or configurations will be omitted so as not to obscurethe gist of the present invention.

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a first embodiment of thepresent invention. As illustrated in FIG. 1, the imaging lens unitaccording to the first embodiment of the present invention includes, inorder from an object side of an object, which is to be formed as animage, a first lens 10, a second lens 20, a third lens 30, a fourth lens40, a fifth lens 50, a filter 60, and an image sensor 70.

Also, an aperture stop S that adjusts a light amount of incident lightthat is incident from the object to be formed as an image and a focaldepth may be disposed toward the object side to be separated apredetermined distance from the first lens 10.

Accordingly, the light amount of the object to be imaged passes througheach of the first lens 10, the second lens 20, the third lens 30, thefourth lens 40, and the fifth lens 50 to be incident on the image sensor70.

Also, the filter 60 may be formed of an ultraviolet ray blocking filter(IR cut filter), that prevents ultraviolet rays emitted from theincident light that is incident therethrough from being transmitted tothe image sensor 70 disposed on an image side.

In detail, the first lens 10 has positive (+) power, and the second lens20 has negative (−) power, the third lens 30 has negative (−) power, thefourth lens 40 has negative (−) power, and the fifth lens 50 hasnegative (−) power.

Also, the first lens 10 is convex toward the object side, and an Abbenumber v1 of the first lens 10 satisfies the following conditionalexpression:

50<v1.   Conditional expression (1):

Also, the second lens 20 is concave toward the image side, and an Abbenumber v2 of the second lens 20 satisfies the following conditionalexpression:

0<v2<30.   Conditional expression (2):

Also, the fourth lens 40 is concave toward the image side and has ameniscus shape, and an Abbe number v4 of the fourth lens 40 satisfiesthe following conditional expression:

0<v4<30.   Conditional expression (3):

Also, the fifth lens 50 has an inflection point toward the image side.

In addition, the second lens 20 and the fourth lens 40 are made of ahigh dispersion material.

The imaging lens unit according to the first embodiment of the presentinvention illustrated in FIG. 1 satisfies the above-describedconditional expressions (1), (2), and (3), and also satisfies thefollowing conditional expressions, thus providing excellent aberrationcharacteristics and high resolving power.

0<(r7+r8)/(r7−r8)<−2.5   Conditional expression (4):

0<tt/f<1.3   Conditional expression (5):

0.7<(v1+v2)/(v3+v4)<1.0   Conditional expression (6):

Here, the symbols denote the following:

f: total focal length of the imaging lens unit

r7: curvature radius of the fourth lens 40 at the object side

r8: curvature radius of the fourth lens 40 at the image side

tt: distance between a vertex of the first lens 10 at the object sideand the image side

v1: Abbe number of the first lens 10

v2: Abbe number of the second lens 20

v3: Abbe number of the third lens 30

v4: Abbe number of the fourth lens 40

Also, aspheric constants of the imaging lens unit according to the firstembodiment of the present invention may be obtained using Equation 1below.

$\begin{matrix}{{Z(h)} = {\frac{c\; h^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}h^{2}}}} + {A\; h^{4}} + {B\; h^{6}} + {C\; h^{8}} + {D\; h^{10}} + {E\; h^{12}} + {F\; h^{14}}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Z: distance from a vertex of a lens to an optical axis direction

c: basic curvature of a lens

h: distance from a vertex of a lens to a direction perpendicular to theoptical axis

K; Conic constant

A, B, C, D, E, F: aspheric constants

Here, the alphabet E used with a conic constant K or with an asphericconstant A, B, C, D, E, or F and a number connected to the alphabet E bya hyphen “-” denote the involution of 10.

For example, “E+01” denotes 10¹, and “E-01” denotes 10⁻¹.

Table 1 below shows design data of the lenses of the imaging lens unitaccording to the first embodiment of the present invention.

TABLE 1 Lens Lens surface Curvature Thickness Abbe number number radius(mm) (mm) Index number First lens S1 1.763 0.900 1.534 56.200 S2 −5.6720.063 Second lens S3 −9.198 0.364 1.614 25.600 S4 4.163 0.308 Third lensS5 14.875 0.551 1.534 56.200 S6 11.495 0.305 Fourth lens S7 −4.748 0.9001.614 25.600 S8 −5.587 0.058 Fifth lens S9 2.809 0.900 1.534 56.200 S101.784 0.300 Filter S11 000 0.300 1.517 64.197 S12 000 0.700

As shown in Table 1, an Abbe number v1 of the first lens 10 according tothe first embodiment of the present invention is 56.200, thus satisfyingConditional expression (1).

Also, an Abbe number v2 of the second lens 20 is 25.600, thus satisfyingConditional expression (2).

Also, an Abbe number v4 of the fourth lens 40 is 25.600, thus satisfyingConditional expression (3).

In addition, it can be seen from a curvature radius of the fourth lens40 that Conditional expression (4) is satisfied.

In addition, it can be seen from Abbe numbers of the first lens 10, thesecond lens 20, and the fourth lens 40 that Conditional expression (6)is satisfied.

Table 2 below shows aspheric constants of the lenses of the imaging lensunit according to the first embodiment of the present invention.

TABLE 2 Lens Lens surface number number K A B C D E F First lens S1−1.0691E+00  1.2819E−02 −1.2774E−02 7.1902E−03 −1.9070E−02  S2−3.6984E+01 −7.3735E−03 −7.9849E−02 2.3367E−02 2.6266E−03 Second lens S3 0.0000E+00  7.4005E−02 −7.3221E−02 1.9838E−02 2.5006E−02 S4  1.4763E+01 2.4962E−02  1.1805E−02 −1.7987E−02  1.0340E−02 Third lens S5 0.0000E+00 −6.9792E−02 −7.6877E−03 3.2156E−02 −3.1754E−02  S6 0.0000E+00  6.8123E−03 −8.2799E−02 5.8992E−02 −2.0776E−02  Fourth lensS7 −1.0154E+02 −1.1014E−03 −1.7923E−02 −6.7548E−02  5.6115E−02−1.8166E−02 S8 −7.9624E+00  3.4197E−02 −3.3333E−02 7.9714E−03−6.9532E−04   1.0098E−05 Fifth lens S9 −1.0389E+01 −9.0596E−02 2.2209E−02 −3.7819E−03  5.0937E−04 −4.6163E−05  S10 −6.3248E+00−4.9536E−02  1.1043E−02 −1.9780E−03  1.9725E−04 −9.8808E−06

Below, Table 3 shows focal lengths (Focal Length Tolerance, EFL) of thelenses of the imaging lens unit according to the first embodiment of thepresent invention, and according to the above conditional expressions.

TABLE 3 Lens number Focal length First lens 2.629 Second lens −4.619Third lens −100.407 Fourth lens −87.132 Fifth lens −13.178 Ass'y 4.9455

As shown in Table 3, it can be seen from the focal length of the firstlens 10 according to the first embodiment of the present invention thatConditional expression (5) is satisfied.

FIG. 2 is a graph showing aberrations of the imaging lens unit accordingto the first embodiment of the present invention. As illustrated in FIG.2, the graph shows longitudinal spherical aberration, astigmatic fieldcurves, and distortion.

A Y-axis of the graph of FIG. 2 denotes an image height, and an X-axisdenotes a focal length (unit: mm) and distortion (unit: %).

Also, with regard to interpretation of the graph of FIG. 2, it may beinterpreted that the closer the curves of the graph are to the Y-axis,the better is an aberration correction function. Referring to the graphof FIG. 2, experimental data values measured according to the firstembodiment of the present invention are close to the Y-axis in almostall areas.

Accordingly, the imaging lens unit according to the first embodiment ofthe present invention has excellent characteristics regarding sphericalaberration, astigmatism, and distortion.

FIG. 3 is a graph showing coma aberration of the imaging lens unitaccording to the first embodiment of the present invention. Asillustrated in FIG. 3, aberrations of tangential components and sagittalcomponents of the imaging lens unit were measured according to a fieldheight of an image plane.

With regard to interpretation of the graph of coma aberration, it may beinterpreted that the closer the curves of the graph are to the X-axis ona positive axis and a negative axis, the better is the function ofcorrecting coma aberration. Referring to the graph of FIG. 3,experimental data values measured according to the first embodiment ofthe present invention are close to the X-axis in almost all areas.

Thus, the imaging lens unit according to the first embodiment of thepresent invention provides an excellent coma aberration correctionfunction.

Second Embodiment

FIG. 4 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a second embodiment ofthe present invention. Description of the same or corresponding elementsto those of the previous embodiment will be denoted with the samereference numerals, and description of repeated elements will beomitted. In regard to this, the imaging lens unit according to thesecond embodiment of the present invention will be describedhereinafter.

As illustrated in FIG. 4, the imaging lens unit according to the secondembodiment of the present invention includes, in order from an objectside of an object which is to be formed as an image, a first lens 10 b,a second lens 20 b, a third lens 30 b, a fourth lens 40 b, a fifth lens50 b, a filter 60, and an image sensor 70.

In detail, the first lens 10 b has positive (+) power, and the secondlens 20 b has negative (−) power, third lens 30 b has positive (+)power, the fourth lens 40 b has negative (−) power, and the fifth lens50 b has negative (−) power.

Also, the filter 60 and the image sensor 70 are arranged at the back ofthe fifth lens 50 b.

Also, an aperture stop S that adjusts a light amount of incident lightincident from an object to be formed as an image and a focal depth maybe disposed toward the object side to be separated at a predetermineddistance from the first lens 10 b.

Table 4 below shows design data of the lenses of the imaging lens unitaccording to the second embodiment of the present invention.

TABLE 4 Lens Lens surface Curvature Thickness Abbe number number radius(mm) (mm) Index number First lens S1 1.816 0.900 1.534 56.200 S2 −5.5470.054 Second lens S3 −97.166 0.400 1.614 25.600 S4 2.856 0.361 Thirdlens S5 −8.294 0.525 1.534 56.200 S6 −4.105 0.272 Fourth lens S7 −2.5840.900 1.614 25.600 S8 −3.098 0.150 Fifth lens S9 3.311 0.900 1.53456.200 S10 1.662 0.300 Filter S11 0.300 1.517 64.197 S12 0.700

Table 5 below shows aspheric constants of the lenses of the imaging lensunit according to the second embodiment of the present invention.

TABLE 5 Lens Lens surface number number K A B C D E F First lens S1−1.0273E+00 1.3839E−02 −9.1788E−03 8.0117E−03 −1.4801E−02  S2−2.9977E+01 1.6039E−02 −7.8975E−02 1.8846E−02 2.9650E−04 Second lens S3 0.0000E+00 4.0689E−02 −5.3059E−02 1.1937E−03 2.1356E−02 S4  5.3062E+00−1.8141E−02   2.2376E−02 2.7022E−02 1.1053E−02 Third lens S5  0.0000E+00−3.5015E−02  −2.0312E−02 3.5575E−02 −2.2585E−02  S6  0.0000E+005.6233E−02 −1.2617E−01 7.4023E−02 −2.0183E−02  Fourth lens S7−2.3140E+01 1.0244E−02 −4.6689E−02 3.7693E−02 3.8980E−02 1.3645E−02 S8−1.6824E+01 1.8939E−02 −2.9754E−02 7.9458E−03 −8.5824E−04  4.4694E−05Fifth lens S9 −1.2507E+00 −1.0725E−01   2.3608E−02 3.6392E−03 4.5632E−042.9218E−05  S10 −6.5984E+00 −3.9477E−02   7.0115E−03 1.0061E−036.4242E−05 1.6654E−06

Below, Table 6 shows focal lengths (Focal Length Tolerance, EFL) of thelenses of the imaging lens unit according to the second embodiment ofthe present invention and according to the above conditionalexpressions.

TABLE 6 Lens number Focal length First lens 2.629 Second lens −4.619Third lens 14.584 Fourth lens −75.715 Fifth lens −7.714 Ass'y 4.9479

FIG. 5 is a graph showing aberrations of the imaging lens unit accordingto the second embodiment of the present invention. As illustrated inFIG. 5, the graph shows longitudinal spherical aberration, astigmaticfield curves, and distortion.

A Y-axis of the graph of FIG. 5 denotes an image height, and an X-axisdenotes a focal length (unit: mm) and distortion (unit: %).

Also, with regard to interpretation of the graph of FIG. 5, it may beinterpreted that the closer the curves of the graph are to the Y-axis,the better is an aberration correction function. Referring to the graphof FIG. 5, experimental data values measured according to the secondembodiment of the present invention are close to the Y-axis in almostall areas.

Accordingly, the imaging lens unit according to the second embodiment ofthe present invention has excellent characteristics regarding sphericalaberration, astigmatism, and distortion.

FIG. 6 is a graph showing coma aberration of the imaging lens unitaccording to the second embodiment of the present invention. Asillustrated in FIG. 6, aberrations of tangential components and sagittalcomponents of the imaging lens unit were measured according to a fieldheight of an image plane.

With regard to interpretation of the graph of coma aberration, it may beinterpreted that the closer the curves of the graph are to the X-axis ona positive axis and a negative axis, the better is the function ofcorrecting coma aberration. Referring to the graph of FIG. 6,experimental data values measured according to the second embodiment ofthe present invention are close to the X-axis in almost all areas.

Thus, the imaging lens unit according to the second embodiment of thepresent invention provides an excellent coma aberration correctionfunction.

Third Embodiment

FIG. 7 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a third embodiment of thepresent invention. Description of the same or corresponding elements tothose of the previous embodiments will be denoted with the samereference numerals, and description of repeated elements will beomitted. In regard to this, the imaging lens unit according to the thirdembodiment of the present invention will be described hereinafter.

As illustrated in FIG. 7, the imaging lens unit according to the thirdembodiment of the present invention includes, in order from an objectside of an object which is to be formed as an image, a first lens 10 c,a second lens 20 c, a third lens 30 c, a fourth lens 40 c, a fifth lens50 c, a filter 60, and an image sensor 70.

In detail, the first lens 10 c has positive (+) power, and the secondlens 20 c has negative (−) power, third lens 30 c has negative (−)power, the fourth lens 40 c has negative (−) power, and the fifth lens50 c has negative (−) power.

Also, an aperture stop S that adjusts a light amount of incident lightincident from an object to be formed as an image and a focal depth maybe disposed between the first lens 10 c and the second lens 20 c.

Also, the filter 60 and the image sensor 70 are arranged at the back ofthe fifth lens 50 c.

Table 7 below shows design data of the lenses of the imaging lens unitaccording to the third embodiment of the present invention.

TABLE 7 Lens Lens surface Curvature Thickness Abbe number number radius(mm) (mm) Index number First lens S1 1.730 0.752 1.534 56.200 S2 −8.5690.050 Aperture stop S3 INFINITY 0.061 Second lens S4 −13.180 0.400 1.61425.600 S5 3.528 0.620 Third lens S6 5.570 0.400 1.534 56.200 S7 4.9200.307 Fourth lens S8 −4.191 0.900 1.614 25.600 S9 −5.275 0.050 Fifthlens S10 2.036 0.855 1.534 56.200 S11 1.702 0.300 Filter S12 0.300 1.51764.197 S13 0.700

Table 8 below shows aspheric constants of the lenses of the imaging lensunit according to the third embodiment of the present invention.

TABLE 8 Lens Lens surface number number K A B C D E F First lens S1−9.4427E−01  1.5322E−02 −8.2026E−03  9.9253E−03 −1.7307E−02  S2 5.7561E+00  2.3480E−03  7.0525E−03 −4.8277E−02 1.8181E−02 Aperture stopS3 Second lens S4  0.0000E+00  2.5677E−02  3.7071E−02 −6.9411E−024.4068E−02 S5  8.7002E+00 −6.2934E−04  4.2185E−02  4.2185E−02 3.0125E−02Third lens S6  0.0000E+00 −8.9747E−02 −3.8532E−02  5.7459E−02−3.3302E−02  S7  0.0000E+00 −1.1576E−02 −1.0527E−01  7.4150E−02−1.9678E−02  Fourth lens S8 −7.0912E+01  4.3019E−02 −3.8067E−02−4.4898E−02 4.3045E−02 −1.0699E−02 S9 −2.0574E+01  3.9125E−02−3.4167E−02  8.2237E−03 −6.7424E−04  −8.5788E−06 Fifth lens  S10−4.0068E+00 −7.0899E−02  2.0161E−02 −4.0410E−03 4.8831E−04 −2.4990E−05 S11 −4.8559E+00 −4.3280E−02  9.4989E−03 −1.5821E−03 1.2507E−04−4.0178E−06

Table 9 below shows focal lengths (Focal Length Tolerance, EFL) of thelenses of the imaging lens unit according to the third embodiment of thepresent invention and according to the above conditional expressions.

TABLE 9 Lens number Focal length First lens 2.766 Second lens −4.492Third lens −100.348 Fourth lens −48.560 Fifth lens −180.664 Ass'y 4.9446

FIG. 8 is a graph showing aberrations of the imaging lens unit accordingto the third embodiment of the present invention. As illustrated in FIG.8, the graph shows longitudinal spherical aberration, astigmatic fieldcurves, and distortion.

A Y-axis of the graph of FIG. 8 denotes an image height, and an X-axisdenotes a focal length (unit: mm) and distortion (unit: %).

Also, with regard to interpretation of the graph of FIG. 8, it may beinterpreted that the closer the curves of the graph are to the Y-axis,the better is an aberration correction function. Referring to the graphof FIG. 8, experimental data values measured according to the thirdembodiment of the present invention are close to the Y-axis in almostall areas.

Accordingly, the imaging lens unit according to the third embodiment ofthe present invention has excellent characteristics regarding sphericalaberration, astigmatism, and distortion.

FIG. 9 is a graph showing coma aberration of the imaging lens unitaccording to the third embodiment of the present invention. Asillustrated in FIG. 9, aberrations of tangential components and sagittalcomponents of the imaging lens unit were measured according to a fieldheight of an image plane.

With regard to interpretation of the graph of coma aberration, it may beinterpreted that the closer the curves of the graph are to the X-axis ona positive axis and a negative axis, the better is the function ofcorrecting coma aberration. Referring to the graph of FIG. 9,experimental data values measured according to the third embodiment ofthe present invention are close to the X-axis in almost all areas.

Thus, the imaging lens unit according to the third embodiment of thepresent invention provides an excellent coma aberration correctionfunction.

Fourth Embodiment

FIG. 10 is a cross-sectional view schematically illustrating an internalstructure of an imaging lens unit according to a fourth embodiment ofthe present invention. Description of the same or corresponding elementsto those of the previous embodiment will be denoted with the samereference numerals, and description of repeated elements will beomitted. In regard to this, the imaging lens unit according to thefourth embodiment of the present invention will be describedhereinafter.

As illustrated in FIG. 10, the imaging lens unit according to the fourthembodiment of the present invention includes, in order from an objectside of an object which is to be formed as an image, a first lens 10 d,a second lens 20 d, a third lens 30 d, a fourth lens 40 d, a fifth lens50 d, a filter 60, and an image sensor 70.

In detail, the first lens 10 d has positive (+) power, and the secondlens 20 d has negative (−) power, third lens 30 d has positive (+)power, the fourth lens 40 d has negative (−) power, and the fifth lens50 d has negative (−) power.

Also, an aperture stop S that adjusts a light amount of incident lightincident from an object to be formed as an image and a focal depth maybe disposed between the first lens 10 d and the second lens 20 d.

Also, the filter 60 and the image sensor 70 are arranged at the back ofthe fifth lens 50 d.

Table 10 below shows design data of the lenses of the imaging lens unitaccording to the fourth embodiment of the present invention.

TABLE 10 Lens Lens surface Curvature Thickness Abbe number number radius(mm) (mm) Index number First lens S1 1.649 0.692 1.534 56.200 S2 −17.8570.050 Aperture stop S3 INFINITY 0.060 Second lens S4 −33.464 0.400 1.61425.600 S5 3.069 0.660 Third lens S6 5.521 0.435 1.534 56.200 S7 7.2470.324 Fourth lens S8 −2.864 0.838 1.614 25.600 S9 −3.554 0.050 Fifthlens S10 2.093 0.891 1.534 56.200 S11 1.634 0.300 Filter S12 0.300 1.51764.197 S13 0.700

Table 11 below shows aspheric constants of the lenses of the imaginglens unit according to the fourth embodiment of the present invention.

TABLE 11 Lens Lens surface number number K A B C D E F First lens S1−7.3137E−01  2.1043E−02 −2.1087E−03   1.4879E−02 −1.3640E−02  S2 6.3414E401 −9.2536E−03 4.0018E−02 −5.2746E−02 1.1953E−02 Aperture stopS3 Second lens S4  0.0000E+00 −2.5029E−02 8.3666E−02 −9.5937E−024.0994E−02 S5  6.3117E−00 −3.3108E−02 6.4702E−02 −6.4244E−02 3.3962E−02Third lens S6  0.0000E+00 −6.7692E−02 6.4702E−02  5.5436E−02−2.7922E−02  S7  0.0000E+00  2.9193E−02 −1.2470E−01   7.7632E−02−1.8549E−02  Fourth lens S8 −3.3044E+01  5.9958E−02 −4.7098E−02 −3.3764E−02 3.5789E−02 −8.7537E−03 S9 −2.4258E+01  4.0732E−02−3.4555E−02   8.3201E−03 −6.6003E−04  −1.1978E−05 Fifth lens  S10−4.4930E+00 −6.1268E−02 1.7272E−02 −3.9021E−03 5.2804E−04 −2.8354E−05 S11 −6.2953E+00 −3.0681E−02 5.4197E−03 −9.2536E−04 5.8930E−05−8.3315E−07

Below, Table 12 shows focal lengths (Focal Length Tolerance, EFL) of thelenses of the imaging lens unit according to the fourth embodiment ofthe present invention and according to the above conditionalexpressions.

TABLE 12 Lens number Focal length First lens 2.863 Second lens −4.560Third lens 39.909 Fourth lens −44.664 Fifth lens −43.002 Ass'y 4.9475

FIG. 11 is a graph showing aberrations of the imaging lens unitaccording to the fourth embodiment of the present invention. Asillustrated in FIG. 11, the graph shows longitudinal sphericalaberration, astigmatic field curves, and distortion.

A Y-axis of the graph of FIG. 11 denotes an image height, and an X-axisdenotes a focal length (unit: mm) and distortion (unit: %).

Also, with regard to interpretation of the graph of FIG. 11, it may beinterpreted that the closer the curves of the graph are to the Y-axis,the better is an aberration correction function. Referring to the graphof FIG. 11, experimental data values measured according to the fourthembodiment of the present invention are close to the Y-axis in almostall areas.

Accordingly, the imaging lens unit according to the fourth embodiment ofthe present invention has excellent characteristics regarding sphericalaberration, astigmatism, and distortion.

FIG. 12 is a graph showing coma aberration of the imaging lens unitaccording to the fourth embodiment of the present invention. Asillustrated in FIG. 12, aberrations of tangential components andsagittal components of the imaging lens unit were measured according toa field height of an image plane.

With regard to interpretation of the graph of coma aberration, it may beinterpreted that the closer the curves of the graph are to the X-axis ona positive axis and a negative axis, the better is the function ofcorrecting coma aberration. Referring to the graph of FIG. 12,experimental data values measured according to the fourth embodiment ofthe present invention are close to the X-axis in almost all areas.

Thus, the imaging lens unit according to the fourth embodiment of thepresent invention provides an excellent coma aberration correctionfunction.

According to the preferred embodiments of the present invention, as theimaging lens unit including five lenses is provided, a compact opticalsystem that is suitable for portable terminals, a compact camera module,and a high resolving power may be provided.

Although the embodiment of the present invention has been disclosed forillustrative purposes, it will be appreciated that the imaging lens unitaccording to the invention is not limited thereto, and those skilled inthe art will appreciate that various modifications, additions andsubstitutions are possible, without departing from the scope and spiritof the invention.

Accordingly, any and all modifications, variations or equivalentarrangements should be considered to be within the scope of theinvention, and the detailed scope of the invention will be disclosed bythe accompanying claims.

1-17. (canceled)
 18. An image lens unit, comprising: a first lens having positive (+) power and comprising a convex surface on an object side; a second lens having negative (−) power and comprising a concave surface on an image side; a third lens having positive (+) power and being convex in the center toward the image side; a fourth lens being concave in the center toward the object side and convex in the center toward the image side; a fifth lens having negative (−) power and comprising: an object side surface being convex in the center and concave at the periphery; and an image side surface being concave in the center and convex at the periphery; and an aperture stop disposed between the first lens and the second lens to adjust a light amount, wherein an Abbe number v1 of the first lens, an Abbe number v2 of the second lens and an Abbe number v4 of the fourth lens satisfy the following conditional expression: 50<v1 0<v2<30 0<v4<30, and wherein the first lens, the second lens, the third lens, the fourth lens and the fifth lens are arranged in order from the object side to the image side.
 19. The image lens unit of claim 18, wherein the convex surface of the first lens and the concave surface of the second lens are arranged on an optical axis.
 20. The image lens unit of claim 19, wherein: Abbe numbers of the first and third lenses are the same, and refractive indexes of the first and third lenses are the same, and Abbe numbers of the second and fourth lenses are the same, and refractive indexes of the second and fourth lenses are the same.
 21. The image lens unit of claim 19, wherein an Abbe number v1 of the first lens and an Abbe number v3 of the third lens are about 56.2.
 22. The image lens unit of claim 19, wherein an Abbe number v2 of the second lens and an Abbe number v3 of the third lens satisfy the following conditional expression: |v2−v3|>30.
 23. The image lens unit of claim 19, wherein: the first lens, the second lens, the third lens, and the fourth lens are made of a plastic material, and the second and fourth lenses are made of a high dispersion material.
 24. The image lens unit of claim 19, wherein the image lens unit satisfies the following conditional expression: $0.080 < \frac{{ct}\; 3}{f} < 0.112$ where ct3 is a thickness of the third lens, and f is the overall focal distance of the image lens unit.
 25. The image lens unit of claim 19, wherein the image lens unit satisfies the following conditional expression: $0.054 < \frac{d\; 34}{f} < 0.066$ where d34 is a distance from an image-side surface of the third lens to an object-side surface of the fourth lens, and f is the overall focal distance of the image lens unit.
 26. The image lens unit of claim 19, wherein the image lens unit satisfies the following conditional expression: $1.121 < {\frac{r\; 2}{f}} < 3.610$ wherein a radius r2 of curvature of an image-side surface of the first lens, and f is the overall focal distance of the image lens unit.
 27. The image lens unit of claim 19, wherein the image lens unit satisfies the following conditional expression: $0.092 < {\frac{r\; 1}{r\; 2}} < 0.328$ where r1 is a radius of curvature of an object-side surface of the first lens, and r2 is a radius of curvature of an image-side surface of the first lens.
 28. The imaging lens unit of claim 19, wherein: an Abbe number v1 of the first lens, an Abbe number v2 of the second lens, an Abbe number v3 of the third lens, and an Abbe number v4 of the fourth lens satisfy the following conditional expression: 0.7<(v1+v2)/(v3+v4)≦1.0. a total focal length f of the imaging lens unit, and a distance tt on an optical axis from an object-side surface of the first lens to an imaging sensor satisfy the following conditional expression: 0<tt/f<1.3.
 29. An image lens unit, comprising: a first lens having positive (+) power and a biconvex shape; a second lens having negative (−) power and comprising a concave surface on an image side; a third lens having positive (+) power and comprising a convex surface on the image side; a fourth lens being concave in the center toward an object side and convex in the center toward the image side; a fifth lens having negative (−) power and comprising: an object side surface being convex in the center and concave at the periphery; and an image side surface being concave in the center and convex at the periphery; and an aperture stop disposed in front of the first lens to adjust a light amount, wherein an Abbe number v1 of the first lens and an Abbe number v2 of the second lens satisfy the following conditional expression: 50<v1 0<v2<30, and wherein the first lens, the second lens, the third lens, the fourth lens and the fifth lens are arranged in order from the object side to the image side.
 30. The image lens unit of claim 29, wherein the biconvex shape of the first lens, the concave surface of the second lens and the convex surface of the third lens are arranged on an optical axis.
 31. The image lens unit of claim 30, wherein a focal distance f1 of the first lens satisfies the following conditional expression: 2.629 mm≦f1≦2.863 mm.
 32. The image lens unit of claim 30, wherein the image lens unit satisfies the following conditional expression: ${- 3.609} < \frac{r\; 2}{f} < {- 1.122}$ where r2 is a radius of curvature of an image-side surface of the first lens, and f is the overall focal distance of the image lens unit.
 33. The image lens unit of claim 30, wherein the image lens unit satisfies the following conditional expression: $0.080 < \frac{{ct}\; 3}{f} < 1.112$ where ct3 is a thickness of the third lens, and f is the overall focal distance of the image lens unit.
 34. The image lens unit of claim 30, wherein the image lens unit satisfies the following conditional expression: ${- 0.831} < \frac{{r\; 1} + {r\; 2}}{{r\; 1} - {r\; 2}} < {- 0.506}$ where r1 is a radius of curvature of an object-side surface of the first lens, and r2 is a radius of curvature of an image-side surface of the first lens.
 35. The image lens unit of claim 30, wherein a distance d12 from an image-side surface of the first lens to an object-side surface of the second lens satisfies the following conditional expression: 0.054 mm≦d12≦0.111 mm.
 36. The image lens unit of claim 30, wherein the image lens unit satisfies the following conditional expression: $0.010 < \frac{d\; 12}{f} < 0.023$ $0.010 < \frac{d\; 45}{f} < 0.031$ where d12 is a distance from an image-side surface of the first lens to an object-side surface of the second lens, d45 is a distance from an image-side surface of the fourth lens to an object-side surface of the fifth lens, and f is the overall focal distance of the image lens unit.
 37. The image lens unit of claim 30, wherein the image lens unit satisfies the following conditional expression: $0.020 < \frac{d\; 12}{f\; 1} < {0.041 - 0.145} < \frac{d\; 23}{f\; 2} < {- 0.066}$ where d12 is a distance from an image-side surface of the first lens to an object-side surface of the second lens, d23 is a distance from an image-side surface of the second lens to an object-side surface of the third lens, f1 is a focal distance of the first lens, and f2 is a focal distance of the second lens.
 38. The lens module of claim 30, wherein a thickness ct3 of the third lens satisfies the following conditional expression: 0.4 mm≦ct3≦0.551 mm.
 39. The image lens unit of claim 30, wherein a radius r1 of curvature of an object-side surface of the first lens, a radius r2 of curvature of an image-side surface of the first lens, and a radius r10 of curvature of an image-side surface of the fifth lens satisfy the following conditional expression: 1.649 mm≦r1≦1.816 mm −17.857 mm≦r2≦−5.547 mm 1.634 mm≦r10≦1.784 mm.
 40. The image lens unit of claim 39, wherein a radius r3 of curvature of an object-side surface of the second lens satisfies the following conditional expression: 9.198 mm≦|r3|≦97.166 mm.
 41. The image lens unit of claim 30, wherein the image lens unit satisfies the following conditional expression: $1.859 < {\frac{r\; 3}{f}} < 19.638$ where r3 is a radius of curvature of an object-side surface of the third lens, and f is the overall focal distance of the image lens unit.
 42. The lens module of claim 30, wherein the lens module satisfies the following conditional expression: $0.092 < {\frac{r\; 1}{r\; 2}} < 0.328$ $2.209 < {\frac{r\; 3}{r\; 4}} < 34.022$ where r1 is a radius of curvature of an object-side surface of the first lens, and r2 is a radius of curvature of an image-side surface of the first lens, r3 is a radius of curvature of an object-side surface of the second lens, and r4 is a radius of curvature of an image-side surface of the second lens.
 43. The imaging lens unit of claim 30, wherein: an Abbe number v1 of the first lens, an Abbe number v2 of the second lens, an Abbe number v3 of the third lens, and an Abbe number v4 of the fourth lens satisfy the following conditional expression: 0.7<(v1+v2)/(v3+v4)≦1.0, and a total focal length f of the imaging lens unit and a distance tt on an optical axis from an object-side surface of the first lens to an imaging sensor satisfy the following conditional expression: 0<tt/f<1.3.
 44. The image lens unit of claim 30, wherein an Abbe number of the first lens, an Abbe number of the third lens and an Abbe number of the fifth lens are about 56.2.
 45. The image lens unit of claim 30, wherein: the first lens, the second lens, the third lens, and the fourth lens are made of a plastic material, the second lens is made of a high dispersion material, and Abbe numbers of the first, third and fifth lenses are the same, and refractive indexes of the first, third and fifth lenses are the same.
 46. The imaging lens unit of claim 30, wherein a radius of curvature of an object-side surface of the first lens is about 1.8 mm, and a radius of curvature of an image-side surface of the fifth lens is about 1.66 mm.
 47. The image lens unit of claim 30, wherein an Abbe number v2 of the second lens and an Abbe number v3 of the third lens satisfy the following conditional expression: |v2−v3|>30. 